Many systems today require different system operating values to be changed where each of these operating values are independently changed by a different control input where the control inputs can be changed independently of each other. The change of one of the system operating values as a function of the change in its control input may be linear or non-linear. Frequently such non-linear function is monotonic. One of the frequently encountered ways of providing the control input to change a system operating value is through a control member which is physically displaced relative to some reference point. The change of any particular operating value in response to a prescribed displacement of its associated control member relative to the reference point associated therewith may be different not only for the different operating values but also may be different at different positions within the quantity range of the operating value controlled by its associated control member where the functional relationship between the operating value and its control member is monotonic. It is frequently desirable to reduce the number of degrees of freedom in the system so as to maintain the ratio between these different operating values constant while each of the different operating values is changed in response to changes in its associated control input. Because the change of the different operating values in response to changes in their associated control inputs may be different, it does not suffice either to directly and rigidly connect the control members directly providing the control inputs or to maintain a fixed ratio between the control inputs to maintain the desired constant ratio between the operating values. By way of an example using physical displacement of independent control members to independently change different system operating values independently of each other, it is desirable on occasion when using a camera zoom lens to both keep the object in focus and keep the image size constant even though the distance between the object being photographed and the camera is changing. Another example is in a paint mixing machine using the three primary color pigments of red, yellow and blue where the desired color has been obtained in a small quantity of paint mixed using a prescribed ratio between the primary color pigments and it is desirable to mix a larger quantity of paint with the same primary color pigment ratio. Presently there is no mechanism to reduce the number of degrees of freedom in the control of a system necessary to achieve the desired result.